Fan and fold head lead termination method using flex cable with edge termination pads

ABSTRACT

An actuator structure includes a flexure suspension with a flag appendage having a cantilevered portion extending parallel to the arm-suspension to form a gap therebetween. The flex cable that connects to the device electronics has an elongated portion secured to the side of the arm-suspension assembly presenting termination pads, which extend to the cable edge, along the elongated portion side and in alignment with the gap between arm-suspension and flag. The leads extending from the transducer are fanned out and extend across the gap. The leads are bonded to the arm-suspension and to the lead cantilevered portion immediately adjoining the gap. To terminate the leads, the flag is folded down 90 degrees, bringing the leads into contact with the te nation pads where they are ultrasonically bonded. The flag is then bent toward its original position causing the fine lead wires to separate between the flag cantilever portion bond and the ultrasonically bonded termination. As the flag is bent back, the fragile connections, between flag and flexure, rupture and the flag is separated from the balance of the arm-suspension assembly. In the assembled condition, the bonding of the fanned out lead wires to the arm-suspension provides strain relief.

This is a Division of application Ser. No. 08/457,515, filed Jun. 1,1995, now U.S. Pat. No. 5,903,413.

FIELD OF THE INVENTION

The present invention pertains to rigid disk data storage devices andmore particularly to a method and structure for terminating leads tointerconnect the transducer with the device data handling electronics.

BACKGROUND OF THE INVENTION

Rigid disk data storage devices are ubiquitous in computer dataprocessing systems and have become a highly competitive commodityproduct which must be economically produced in an environment of rapidtechnology advance and short product development cycles. Data integrityand device reliability must be retained while achieving both higher dataareal densities and reduced device size. Enhanced structural designsenabled by improved fabrication techniques afford a competitiveadvantage in lager drives using a 31/2 inch or 21/2 inch form factor,but become essential as miniaturization progresses to the PersonalComputer Memory Card is Industry Association (PCMCIA) type II standardwherein the overall dice size has respective approximate length andwidth dimensions of 31/4 and 2 inches and an overall height of 5millimeters. In addition, it can be expected that even smaller deviceswill be used in the future.

No portion of the disk drive presents greater mechanical challenges thanthe actuator assembly wherein the transducer, which is moved rapidlyfrom track to track during access and is maintained in precisionalignment with an addressed track during data read and write operations,must be electrically connected to the arm electronics.

The connecting lead wires, which carry the read/write electricalsignals, are less than 0.0002 inch in diameter and require attachment toboth the transducer and the flex cable that electrically connects theactuator to the drive circuitry. Further, multiple leads are necessaryfor each transducer head since the state of the art device for enablinghigh density recording is the magnetoresistive (MR) head which isactually two transducer devices, an MR transducer for reading data and athin film transducer for writing data The attachment of lead wires toboth the transducer head and the flex cable, previously accomplished bylargely manual soldering techniques, has been enhanced by positioningand alignment structures and methods that better adapt to automaticfabrication using ultrasonic bonding. Such an improved process andstructure is shown in U.S. Pat. No. 5,074,029 (Brooks, Jr. et al.)assigned to the assignee of the present invention.

The cited patent teaches the use of a plastic tail portion that ismolded about the end of the transducer supporting load beam to provide awindow across which the lead wires are strung and positioned to permitpivotal movement of the wires spanning the window into alignment withflex cable contact pads to achieve the electrical connections. Theplastic tail portion is progressively removed from the load beam andfollowing the ultrasonic welding of the lead portions spanning thewindow to the corresponding flex cable pads, the last portion is rammedso that no part, of the tail portion form a part of the final assembly.This structure and technique enables the multiple leads to be alignedand attached in a single operation using smaller pad areas. However, theuse of an intermediate part not only increases the cost, but also thecumulative tolerances involved including the pivoting of the positionedleads requires that the alignment of wires and pads be carefully checkedprior to the final welding attachment operation.

SUMMARY OF THE INVENTION

In the structure of the present invention, an assembly is formed bylaser welding the load beam/flexure, which supports the transducer headat the distal end, to the rigid actuator am A flag portion, formed as anintegral part of the load beam/flexure, is used to retain the lead wiresfrom the transducer in a fanned out orientation. The leads in the spacedapart, fanned out orientation extend across the space between the flagcantilevered portion and the flexure-arm assembly and are bonded to boththe flexure-arm assembly immediately adjacent the edge of suchflexure-arm assembly and to the flag cantilevered portion. The flexcable is supported along the side of the actuator arm in a planesubstantially perpendicular to the plane defined by the fanned out leadswit terminal pads respectively aligned with the respective fanned outleads. To complete an electrical connection between the lead wires andthe respective terminal pads, the flag is turned or bent 90 degrees tobring the lead portions between the flexure-arm assembly and the flaginto a contacting, overlying position with the flex cable terminal pads.Ultrasonic bonding then effects both the removal of the insulatingcoating on the lead wires and electrically and mechanically securing thelead wires to the respective terminal pads.

The flag portion is tenuously attached to remainder of the flexureelement and designed to fatigue after two 90 degree bends. The flag isfirst bent 90 degrees to bring the lead wires into contact with the flexcable terminal pads. Following the laser welding operation, the flag isbent upward toward the original coplanar relation with the remainder ofthe flexure which causes the fragile lead wires to break beyond thelaser weld and the flag to separate from the balance of the flexure.Each of the lead wires is now bonded and stress relieved at the edge ofthe flexure-arm assembly with the portion extending therebeyond turnedat substantially a right angle and terminating in a welded connectionwith a flex cable terminal pad.

The lead wire to flex cable connection is completed without using anintermediate part that not only increases cost but also adds cumulativetolerances which require careful alignment prior to welding andincreases the number of erroneous connections that must be reworked.Further, the flex cable, extending along the arm at substantially aright angle to the plane determined by the fanned lead wires extendingto the flag, enables the use of larger terminal pads along the flexcable margins rather than small terminal pads closely confined at thecable end, further reducing the opportunity for misregistration betweenlead wire and terminal pad.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an arm suspension assembly with the flexure including theflag appendage utilized in the present invention.

FIG. 2 shows a flex cable elongated element that is attached to anarm-suspension assembly and presents termination pads along the sidesthat extend to the cable edge.

FIG. 3 illustrates a rotary actuator armature assembly including an armwith a pair of flexures attached and including flag appendages forterminating transducer leads to the flex cable and the driveelectronics.

FIG. 3A is a broken away partial elevation of the actuator armature ofFIG. 3 showing the ration pads following removal of the flag.

FIG. 4 shows broken away portions of arm-suspensions, disks and a flexcable with three elongated portions illustrating the invention in theenvironment of a multi disk drive.

FIG. 5 is an exploded view of a PCMCIA type II rigid disk data storagedevice.

DETAILED DESCRIPTION

FIGS. 1, 2 and 3 illustrate a partial actuator assembly incorporatingthe present invention in the environment of a single disk rigid diskdrive. FIG. 1 includes an arm 10 and attached load beam-flexuresuspension 11 for supporting a transducer head 13 and also shows leadwires 14 extending from the transducer head. FIG. 2 shows a portion ofthe flex cable including the termination pads to which the lead wiresfrom the transducer head are electrically connected. FIG. 3 is anassembly including two arm-suspension assemblies separated by a spacerwhich carries the voice coil all of which are supported about the outerrace of a bearing and flier includes the flex cable end portion whichhas terminal pads aligned with the lead wires prior to the final stepsduring which the leads are soldered or ultrasonically bonded to therespective termination pads.

In FIG. 1 the substantially rigid actuator arm 10 includes a circularopening 15 through which is received the bearing about which theactuator armature assembly pivots. A load beam-flexure suspension 11 isattached to arm 10 by laser welds at nine sites 16 as shown in thefigure. Suspension 11 includes a pair of flanges 18 which add rigidityto the flexure portion extending from arm 10. Intermediate the flangedportion and the locations of welded attachment to arm 10 the suspensionis flat is with a central opening 19 to provide flexibility for onedegree of freedom allowing the transducer head at the distal end of thesuspension to rise and fall. Transducer head 13 is mounted adjacent thedistal end of suspension 11 in a manner to afford pitch and roll of thehead during relative motion between the head and the confronting,rotating data disk surface. Suspension 11 also includes a flag appendage20 including a cantilevered portion 21 extending substantially parallelto the arm edge 22 and forming a gap therebetween. The flag 20 is joinedto the balance of the suspension 11 by tenuous and fragile connectingportions 24 which are separated by an opening 25. The connectingportions 24 between flag 20 and the balance of suspension 11 directlyoverlie the edge of arm 10 and are designed to fatigue and fracturefollowing two 90 degree bends of the flag appendage.

Signals to and from the transducer travel over lead wires 14 whichterminate at one end in connections to the transducers supported onslider or head 13. The state of the art device for reading and recordingdata in the environment of very high density magnetic storage devices isa magnetoresistive (MR) head. Such a device is effectively twotransducers since a thin film transducer is used to write data and an MRtransducer is used for reading data. Accordingly, four leads are used toconnect the transducers of the MR head to the device electronics. Thefour lead wires extending from the transducer are secured to thesuspension by tacking with minuscule amounts of fast curing ultra violet(UV) adhesive at three locations 26. The lead wires 14 thereafter turnand are fanned out such that the four wires extend over the gap betweenarm 10 and cantilevered portion 21 with the same spacing as existsbetween the centerlines of the flex cable termination pads. The leadwires 14 are retained in the separated orientation by applyingcontinuous strips of UV adhesive 27, 28 on the arm 10 and, as shown, tothe flag by individual adhesive bonds 29. In practice, it is equallylikely that a continuous strip of adhesive would be used on cantileveredportion 21 (as shown in FIG. 3). With the lead wires spanning the gapbetween bond sites 28 and 29, the wire portions in the gap can bestripped of insulation using laser technology to afford a more positiveelectrical connection when subsequently ultrasonically bonded to theterminal pad.

FIG. 2 shows that portion of the flex cable to which the lead wires fromthe transducers are connected. The portion of cable 32 illustratedincludes ten longitudinally extending conductors that provide fortransmission of signals to and from two transducers (which accessopposite sides of a single disk) and for power to the voice coil thatpivots the actuator. Cable termination pads 34, 35, 36 and 37 terminatelead wires from one transducer, while pads 34', 35', 36' and 37'terminate the lead wires from a second transducer. Leads 38, 39 areconnected to the actuator voice coil (shown in FIG. 3) and a ground lead40 resides between conductors leading to the voice coil and the signallines communicating with the transducers. It will also be noted that asingle conductor is connected to both read ground termination pads 34,34'. By placing the termination pads along the margins of the flex cablerather than at the end, the pad size can be substantially enlarged. Theflex cable termination pads and conductors are arranged to providemaximum pad size for soldering or ultrasonic bonding (the conductorshave minimum spacing and the pads extend all the way to the cable edge).The common read ground and termination pad arrangement also minimizesthe overall width of thee flex and bond area (reducing the overallassembly height or in the environment of a multiple disk drive, the diskto disk spacing).

The showing of FIG. 3 is an actuator armature assembly with a first,upper arm-suspension assembly 41 as seen in FIG. 1 and a second, lowerarm-suspension assembly 42 which is a mirror image or "reverse plan" ofthe upper assembly 41 to present both sets of terminal leads and flagappendages at the same assembly side for connection to upper and lowertermination pads of the same flex cable 32. The arm-suspensionassemblies 41, 42 are axially separated by a spacer 44 and clamped orsecured together and to the outer race 45 of bearing 46 for unitarypivotal movement about the axis of bearing 46. The spacer 44 also hassecured thereto, a pair of arms 48, 49 which are bonded to and supportthe voice coil 50. The voice coil leads 38, 39 and ground lead 40 arefolded beneath the armature assembly, as shown. The voice coil flexcable conductors extend around the bearing to present termination padsto which the ends of the voice coil are connected. Flex cable 32 restsagainst a stiffener plate 51 to which it is secured at the distal end inthe region of the termination pads 34 trough 37. The length of contactbetween stiffener plate 51 and flex cable 32 is a function of therotational position of the actor armature. As the armature moves in aclockwise direction, as viewed in FIG. 3, the length of contactdecreases and when moving in a counterclockwise dion, the length ofcontact increases. The backing plate or stiffener 51 is secured to theupper and lower actuator arms 10 and 10' and alignment between terminalpads and lead wires is established by bonding stiffener 51 to arms 10,10' while the end of the stiffener is abutting arm and suspensionflexure edge surface 53.

The connection of lead wire portions in the gap between bond sites 28and 29 to the respective termination pads 34 through 37 is accomplishedby bending the upper flag 20 downward 90 degrees about an axisestablished by the weakened flag connections 24. With the leadsoverlying the respective termination pads, electrical connection is madeby ultrasonic bonding of lead to pad. Following lead attachment at therespective termination pad, the flag appendage 20 is bent upward. Thelead wires 14, being very small and ductile, readily separate betweenthe ultrasonic bond and the bond site 29 on the flag cantileveredportion 21. As flag 20 pivots upwardly, the fragile connecting portions24 securing the flag to the balance of flexure 11 fatigue and theappendage breaks away. Thereafter, the lower flag 20' is bent upward toalign lead wires and termination pads, the leads are ultrasonicallybonded and the appendage is turned downward to separate the flag fromboth the lead wires and the lower flexure. FIG. 3A illustrates thetermination pads of flex cable 32 following removal of the flagappendages 20 and 20'.

The showing of FIG. 4 is similar to the illustrations of the earlierfigures and is presented to illustrate the application of the inventionto multiple disk drives. The actuator assembly includes sixarm-suspension assemblies 56 which support transducers that write datato and read data from the six surfaces presented by three disks 57. Theflex cable 58 includes three projecting portions 59, each of whichpresent termination pads 60 along each side as in the cable portion ofFIG. 2 to terminate lead wires from the six transducers.

Manual lead routing and manual soldering techniques are the largestsingle sources of actuator build defects. Such procedures use tapes toretain lead wires. The dispensing, handling and removal of such tapesplus the damage introduced by the necessity of handling fragile leadswith tweezers and the mispositioning of lead wires during routing allreduce the yield of acceptable, functional devices. Compared with theuse of a molded flag appendage and ultrasonic welding, the presentstructure (a metal flag formed integrally with the flexure member) usesa simplified stringing path and folds the wires perpendicular to thetermination pads and is thus less sensitive to flex cable and flagpositioning. Thus, no special tooling is required to assure precisionalignment. The structure shown and described is adaptable to eithermanual or automated actuator build processes.

FIG. 5 is an exploded view illustrating a PCMCIA type II disk drive.Primary support is provided by base 62 with the enclosure completed by acover 63 and gasket 64 secured to the base by a series of screws 65. Theprincipal electronic components are mounted on the electronic carrierassembly 66 which has an end extending outside the enclosure andterminating in a connector 67. The disk 68 surrounds the spindle motor69 and is clamped to the motor rotor portion by clamp 70. The actuatorarmature 71, which supports a pair of MR heads on flexures that areconnected to arm 72, is driven by a voice coil 73 and electricallyconnect to the drive electronics on the electronic carrier assembly 66by flex cable 74. The gap, in which the voice coil 73 is positioned, iscreated by magnet 77 supported on pole piece 78 and cover 79, whichserves as the other pole piece, to concentrate magnetic flux in the gap.The post secured to the inner race of bearing 80, about which theactuator armature 71 rotates, is attached to both base 62 and cover 63by screws 81 (one of which is visible). The disk spindle assembly isalso supported by both the base 62 and cover 63 (screw 82). A rampassembly 83 secured to base 62 includes upper and lower ramp elementswhich enable the heads to be lifted away from the disk surface when theactuator is not operating to read and write data. Actuator latch 85secures the actuator armature 71 to retain the transducer heads in theunloaded condition. Since this type of drive is used in portable,battery powered applications, the actuator is moved to a park position,unloading the heads, with great frequency to implement power down whennot reading or writing data and enable energy conservation.

While the invention has been particularly shown and described withreference to a preferred embodiment thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention.

What is claimed is:
 1. A method of assembling an actuator arm/load beamflexure (arm/flexure) assembly to arm electronics electrically connectedto a flex cable which presents termination pads along the sides thereofusing a flag appendage, formed as a unitary part of said flexure andpresents a cantilevered portion separated from the arm/flexure assemblyfor supporting a plurality of lead wires extending from a transducercomprising the steps of:supporting a terminal portion of said flex cableadjacent said actuator arm to position said termination pads along a gapbetween said flag appendage cantilevered portion and [the balance] anedge surface of said arm/flexure assembly; stringing said lead wiresacross said gap in fanned out orientation to effect alignment withrespective termination pads; bonding said lead wires to said arm/flexureassembly at each side of said gap; bending said flag appendage from anoriginal orientation to rotate said lead wires respectively intooverlying, contacting relation to the termination pads; electricallyconnecting said lead wires to the respective aligned termination pads bybonding each of said lead wires to a confronting one of the terminationpads; and removing said flag appendage from said arm/flexure assembly byrotating said flag appendage toward the original orientation to inducefracture of a connection with the flexure and breaking the lead wiresbeyond the gap.
 2. A method for fabricating an actuator arm assembly toa flexible cable comprising:forming a transducer carrying suspensionassembly including a flexure with a flag appendage secured to an edgesurface of said flexure by fragile connecting portions and presenting acantilevered portion; securing said suspension assembly to an actuatorarm with the flag appendage projecting away from an edge of said arm,said connecting portions overlying said edge of said arm and thecantilevered portion extending substantially parallel and spaced fromsaid arm; attaching to said arm an elongated flex cable portion whichpresents a plurality of termination pads at one side thereof which arealigned with a gap between said arm and said flag appendage cantileveredportion; stringing intermediate portions of lead wires along thearm-suspension assembly with terminal portions of the wires fanned outand spanning said gap in respective alignment with said terminationpads; bonding each of the lead wires spanning said gap and aligned witha respective one of said termination pads to both said arm-suspensionassembly and said flag appendage cantilevered portion adjacent said gap;electrically bonding said lead wires spanning said gap respectively tosaid termination pads by bending said flag appendage from an originalorientation to bring the lead wires spanning said gap into contact withthe respective aligned termination pads; and removing said flagappendage from said suspension assembly by bending said flag appendageback toward the original orientation causing the said fragile connectingportions to fatigue and the lead wires to break between the terminationpad bonding site and the flag appendage cantilevered portion.